Mike

Only if it can be jointed to pipes to BS EN 12237 sized joints - which is very unlikely.

Yes if it performs well in the Passivhaus database, which lists models that have been independently tested to more accurate standards than those required in the UK and those used by manufacturers: https://database.passivehouse.com/en/components/list/ventilation_small. Vent-Axia do have 3 models in the database, but the Plus B isn't one of them. BTW, the 'Efficiency Ratio' (which takes into account electricity used as well as heat recovered) is the key figure for comparison. For example, the near-identical Zehnder ComfoAir 200 & 225 models both have a heat recovery rate of 92%, but the 225 has more efficient fans so has a higher Efficiency Ratio (0.69, rather than 0.67).

Cork is expensive, but a remarkable insulation material, however... ...if you have enough depth between the rafters, or are prepared to sacrifice head height, then that would b my preferred option. If it was installed without an external airtightness membrane, then it could be due to air movement.

And there's now another reason to add to the list. It's been reported in France that burgers have been meting PVC windows with a blow torch, so they can access the locking mechanism - https://www.dna.fr/faits-divers-justice/2025/01/28/les-cambrioleurs-faisaient-fondre-les-fenetres (in French)

The French budget, voted through last week, increases VAT on the supply & installation of gas boilers to 20%. It had already risen from 1st January this year from 5.5% to 10%, so a hefty increase, which hasn't been universally welcomed for multiple reasons: https://bati.zepros.fr/actu-generale/budget-2025-mesures-batiment-plutot-bien-accueillies (in French). It would certainly tilt the balance in favour of ASHPs if adopted in the UK (where, I think, they are currently zero-rated but due to revert back to 5% on 1 April 2027).

I liked the look of them too, but decided against them because of the lack of a Coanda effect and lack of 'safe' placement options in my apartment. If you have larger rooms with have enough space to place them carefully, then they're not likely to be a problem. Though, from memory, I don't thing there's Zhender-type sock filter that you can add to them.

It will be a few °C in winter. For a real-life example: "In my bedroom the vent is about 0.5m to the side of the bed head and I only notice it on very cold nights." https://forum.buildhub.org.uk/topic/25366-directional-vents-diffusers/#comment-388570

As you turn down the airflow on a Coanda-effect diffusers the mixing-distance will certainly decrease; no doubt there's a formula out there for that. If you turn down the airflow on a regular diffuser the air will increasingly tend to fall vertically (if it wasn't already being pointing straight down) as cooler air is denser, and you wouldn't want that over (or close-to) a bedhead, for example.

You won't find flush ones, but those from Cavius are (or at least were when I bought mine) marketed as the World's smallest. Some have optional recessed bases to make them even less prominent.

Wall-mounted Coanda effect vents are indeed very useful to protect supply air across large spaces. However domestic ceiling mounted Coanda-effect vents have the opposite effect and a different benefit. They're intended to mix the supply air (which will be a few °C colder than the room temperature in winter), with the room air, while the airspeed drops, the two effects combining together to avoid cool drafts. Here's an example in a domestic-sized room using the Zehnder ZSX 125 Coanda-effect diffuser; the colours show airspeed, but if you mentally swap them round (so blue = warmer & yellow = cooler) that would be more-or-less the temperature distribution. In a small room, especially a bedroom, where you can't avoid having a vent near a bed, that can be pretty useful.

All sounds good. The only reason I chose 'full' plaster was to even-out the undulations in the old brick / stone walls, so that the IWI had a snug fit.

Where I have internal wall insulation I've done similar with the ceiling joists on my current project - though plaster rather than just parge - where they meet brick / stonework. In the unheated & uninsulated entrance lobby the gaps between are filled with FM330 for airtightness. I also have a mansard wall where the joists sit between timber beams above and below. Those have also been foamed with FM330. Both solutions are perfectly airtight.

I'm using the same model and that is indeed their minimum distance. However I've seen it recommended that Coanda-effect vents should be >750mm away from walls, though I can't give you a reference for that. But since they disperse the air across the ceiling in all directions, there is no need to squash them in a corner. I'd prefer that in principle too. However if they don't protrude from the ceiling you don't get the Coanda effect; instead the air will blow in whatever downward direction the vent deflectors dictate, albeit gently. That's not a problem if you have space to site them away from where they may cause a draft, but not so good in a smallish room where you don't have that freedom. At lest the Zehnder Luna protrudes less than most and they look reasonably good.

If you have a stove <5kW, and if it doesn't have a flue draft stabiliser, and if the design air permeability of your house is >5.0m3/{h.m2), and if the manufacturer doesn't say otherwise, then the Building Regs say you don't need a permanent vent. Though why they use the design air permeability instead of the actual air permeability, I don't know. However you are planning to have more than one stove, so logic dictates that you'd need to add the outputs together and still be <5kW - which seems unlikely.

Building Regs Part H, section H3, sets out how to calculate the required gutter capacity. Your chosen gutter manufacturer will have information on the carrying capacity of their gutters when laid flat or to falls & the distance between down pipes. You need to match the two up to get your answer. By using a string line to set out the brackets

Just been looking for an answer to that question and found a partial answer in this guide to BS5250 : https://assets.ctfassets.net/cd81nrotvav2/ujVUWjeQFoihtJkYoWsxY/878731b5e0c188d85afad93ba1dac78b/BMI-BS5250-Pitchedand_flatroofingguidanceAugust2021.pdf Page 7 shows a section of a cold pitched roof with a cold flat roof at the apex - not quite what you have, but on the right lines - that says "If the span of the flat roof apex is more than 5 m then additional ventilation to the cold roof space to a minimum free area of 5,000 mm²/m should be introduced, as close as practicable across the midpoint of the flat roof apex." You'd have to ask if anyone will confirm that as suitable for your monopitch version.

Spit on! I shouldn't rely to stuff at this time of the night...

Why did he design it then?! The best solution would, of course, be switch to a warm roof design. Failing that, you could add breather vents in the flat roof - Klober do a range, for example, but so do others. I'm not sure where the Building Regs have hidden the provisions on ventilating roofs, but it used to require vents equivalent to a % of the roof area in the case of large / complex roofs. If nobody else chips in, then the manufacturer should know, if your architect doesn't.

Me too, for the quality of the finish as much as anything else (provided you find a good plasterer). However well dot & dab is done, you're guaranteed to see the joints in at least some lighting conditions.

I wouldn't put the ceiling supply vents right in the room corners & so close to the walls, particularly in the bedrooms. Many such vents use the Coanda effect (which is recommended) so that the air disperses evenly across the ceiling. However, if a wall is in the way, the air will be deflected down the wall and may cause an unwanted draft; from memory 750mm is the recommended minimum distance from a wall. Zehnder's Luna S (and probably others) have an optional deflector that can be inserted to get around that. What @JohnMo says. Just add a double pipe to the extract over the sink. Zehnder's advice is to place the extract near a shower, but not within / over it.

Good to see the pictures - it looks excellent!

When the storm hits is a great opportunity to detect the leaks - if the wind is strong you'll be able to detect if by feel. Just as useful as a second blower-door test!

Yes, the Regulations require fire door sets; that is a door + frame tested & certified together.

Well it would be against the Building Regulations - though you'd only be prosecuted if you survived the carbon monoxide poisoning. You'd need a 'room sealed' stove installed in according to the manufacturer's guidance - I've only seen horizontal of under-floor supply pipes. The alternative is to knock a hole in the wall and install a permanently-open vent, in accordance with the dimensions in Part J of the Building Regs. If it's only a decorative effect you want, block the flues, install a TV screen inside an old stove and set it to show a flame video.

Sounds good, though I was thinking of something a little different! A sill would normally project through the render, where the red arrow is below (looking at the outside now, not the inside). But if you're rendering before the window's fitted, the render will be in the way, unless you make some provision for it, or have another solution - stone sub-sill maybe?